We investigated infants' sensitivity to amount of continuous quantity and to change in amount of continuous quantity. Using a habituation procedure, Experiment 1 examined whether 6-month-old infants can distinguish between different amounts of liquid in a container. Infants looked significantly longer at a novel quantity than at the familiar quantity. Using a violation-of-expectation paradigm, Experiment 2 examined whether 9-month-old infants expect a change in amount when liquid is added to a hidden container which is already one-fourth full of liquid. Infants looked significantly longer at the impossible event than at the possible event. These findings indicate that infants are sensitive to amount, calling into question claims that infants have a quantitative mechanism which is exclusive to number.